UMMS RESEARCHERS FIND RNA INTERFERENCE EFFECTIVELY SLOWS PROGRESSION OF LOU GEHRIG’S DISEASE

Paper citing results named Journal of Biological Chemistry ‘Paper of the Week’

April 10, 2008

WORCESTER, Mass.—Investigators from the University of Massachusetts Medical School (UMMS) have inhibited a gene (SOD1) that causes a subset of genetically inherited Amyotrophic Lateral Sclerosis (ALS), also known as Lou Gehrig’s Disease, and a delay in the onset of end-stage ALS.

The research was performed by University of Massachusetts Medical School researchers Tariq M. Rana, PhD, professor of biochemistry & molecular pharmacology; Zuoshang Xu, MD, PhD, professor of biochemistry & molecular pharmacology and cell biology; and colleagues, and was supported in part by funding from RXi’s former parent company. Both Drs. Rana and Xu serve are scientific advisors for RXi.

In January 2007, RXi announced that it had entered into an agreement with UMMS to exclusively license the technology described in the published work for potential therapeutic applications. "Based on this work, we believe that long term administration of chemically modified RNAi compounds to the central nervous system has potential promise for the treatment of inherited ALS caused by SOD1 mutations and other chronic central nervous system disorders," said Tod Woolf, PhD, president and CEO of RXi. "RXi is building on this work by converting the siRNA compounds described in the paper into our proprietary rxRNA™ format which we have found to be better tolerated in initial studies."

Results were published in the April 2008 issue of the peer-reviewed Journal of Biological Chemistry (JBC) in the paper, "Therapeutic gene silencing delivered by a chemically modified siRNA against mutant SOD1 slows ALS progression." The paper has been selected as a JBC Paper of the Week. Each week, JBC editorial board members and editors select papers that rank in the top 1 percent of papers they will review in a year in significance and overall importance as Paper of the Week. An abstract of the journal article is available online at http://www.ncbi.nlm.nih.gov/pubmed/18367449?ordinalpos=1&itool= EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum.

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About the University of Massachusetts Medical School
The University of Massachusetts Medical School, one of the fastest growing academic health centers in the country, has built a reputation as a world-class research institution, consistently producing noteworthy advances in clinical and basic research. The Medical School attracts more than $176 million in research funding annually, 80 percent of which comes from federal funding sources. The work of UMMS researcher Craig Mello, PhD, an investigator of the prestigious Howard Hughes Medical Institute (HHMI), and his colleague Andrew Fire, PhD, then of the Carnegie Institution of Washington, toward the discovery of RNA interference was awarded the 2006 Nobel Prize in Physiology or Medicine, hailed as the "Breakthrough of the Year" in 2002 by Science magazine. UMMS is the academic partner of UMass Memorial Health Care, the largest health care provider in Central Massachusetts. For more information, visit www.umassmed.edu.

About RXi Pharmaceuticals Corporation
RXi Pharmaceuticals is a discovery-stage biopharmaceutical company pursuing the development and potential commercialization of proprietary therapeutics based on RNA interference (RNAi) for the treatment of human diseases. RXi Pharmaceuticals' rxRNA™ compounds are distinct from the siRNA compounds used by many other companies developing RNAi therapeutics and are believed by the Company, based on its internal research, to be up to 100x more active than conventional siRNA (depending on the target site), nuclease resistant and readily manufactured. RXi Pharmaceuticals believes it is well positioned to compete successfully in the RNAi-based therapeutics market with its accomplished scientific advisors, including Dr. Craig Mello, recipient of the 2006 Nobel Prize for his co-discovery of RNAi; a management team that is experienced in developing RNAi products; and a strong early intellectual property position.

Forward-Looking Statements
This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Such statements include, but are not limited to, statements about future expectations, plan and future development of RXi Pharmaceutical Corporation’s products and technologies. These forward-looking statements about future expectations, plans and prospects of the development of RXi Pharmaceutical Corporation’s products and technologies involve significant risks, uncertainties and assumptions, including the risk that the development of our RNAi-based therapeutics may be delayed or may not proceed as planned and we may not be able to complete development of any RNAi-based product, the risk that the FDA approval process may be delayed for any drugs that we develop, and the possibility that other companies or organizations may assert patent rights that prevent us from developing our products. Actual results may differ materially from those RXi Pharmaceuticals Corporation contemplated by these forward-looking statements. RXi Pharmaceuticals Corporation does not undertake to update any of these forward-looking statements to reflect a change in its views or events or circumstances that occur after the date of this release.

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Contact: Office of Public Affairs and Publications, 508-856-2000, ummsnews@umassmed.edu